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132-505: Limiting is any process by which the amplitude of a signal is prevented from exceeding a predetermined value. Limiters are common as a safety device in live sound and broadcast applications to prevent sudden volume peaks from occurring. Limiters are also used as protective features in some components of sound reinforcement systems (e.g., powered mixing boards and power amplifiers ) and in some bass amplifiers , to prevent unwanted distortion or loudspeaker damage. Limiting can refer to

264-413: A band-pass filter, eliminating undesirable frequencies both above and below the auditory spectrum. A band-stop filter , does the opposite. It allows all frequencies to pass except for one band in the middle. A feedback suppressor, using an microprocessor , automatically detects the onset of feedback and applies a narrow band-stop filter (a notch filter ) at specific frequency or frequencies pertaining to

396-435: A caveat for a version using a brass rod instead of the needle. Other minor variations and improvements were made to the liquid microphone by Majoranna, Chambers, Vanni, Sykes, and Elisha Gray, and one version was patented by Reginald Fessenden in 1903. These were the first working microphones, but they were not practical for commercial application. The famous first phone conversation between Bell and Watson took place using

528-403: A resonant circuit that modulates the frequency of the oscillator signal. Demodulation yields a low-noise audio frequency signal with a very low source impedance. The absence of a high bias voltage permits the use of a diaphragm with looser tension, which may be used to achieve wider frequency response due to higher compliance. The RF biasing process results in a lower electrical impedance capsule,

660-548: A reverb effect, which outputs a wet (effected) version of the signal, which is typically mixed in varying amounts with the dry (effect-free) signal. Many electronic effects units are used in sound reinforcement systems, including digital delay and reverb . Some concerts use pitch correction effects (e.g., AutoTune ), which electronically correct any out-of-tune singing. Mixing consoles also have additional sends , also referred to as auxes or aux sends (an abbreviation for "auxiliary send"), on each input channel so that

792-406: A "boomy" sounding bass drum , or an overly resonant dreadnought guitar can be cut. Sound reinforcement systems typically use graphic equalizers with one-third octave frequency centers. These are typically used to equalize output signals going to the main loudspeaker system or the monitor speakers on stage. Parametric equalizers are often built into each channel in mixing consoles, typically for

924-592: A 3.5 mm plug as usually used for stereo connections; the ring, instead of carrying the signal for a second channel, carries power. A valve microphone is a condenser microphone that uses a vacuum tube (valve) amplifier . They remain popular with enthusiasts of tube sound . The dynamic microphone (also known as the moving-coil microphone ) works via electromagnetic induction . They are robust, relatively inexpensive and resistant to moisture. This, coupled with their potentially high gain before feedback , makes them popular for on-stage use. Dynamic microphones use

1056-457: A button microphone), uses a capsule or button containing carbon granules pressed between two metal plates like the Berliner and Edison microphones. A voltage is applied across the metal plates, causing a small current to flow through the carbon. One of the plates, the diaphragm, vibrates in sympathy with incident sound waves, applying a varying pressure to the carbon. The changing pressure deforms

1188-446: A crossover to separate the sound into low, middle and high frequencies can lead to a "cleaner", clearer sound (see bi-amplification ) than routing all of the frequencies through a single full-range speaker system. Nevertheless, many small venues still use a single full-range speaker system, as it is easier to set up and less expensive. Many types of input transducers can be found in a sound reinforcement system, with microphones being

1320-441: A diaphragm that is at least partially open on both sides. The pressure difference between the two sides produces its directional characteristics. Other elements such as the external shape of the microphone and external devices such as interference tubes can also alter a microphone's directional response. A pure pressure-gradient microphone is equally sensitive to sounds arriving from front or back but insensitive to sounds arriving from

1452-467: A different mix can be created and sent elsewhere for another purpose. One usage for aux sends is to create a mix of the vocal and instrument signals for the monitor mix (this is what the onstage singers and musicians hear from their monitor speakers or in-ear monitors ). Another use of an aux send is to select varying amounts of certain channels (via the aux send knobs on each channel), and then route these signals to an effects processor. A common example of

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1584-479: A good "ear" for what the music should sound like in order to create a good mix. Multiple consoles can be used for different purposes in a single sound reinforcement system. The front-of-house (FOH) mixing console is typically located where the operator can see the action on stage and hear what the audience hears. For broadcast and recording applications, the mixing console may be placed within an enclosed booth or outside in an OB van . Large music productions often use

1716-435: A high-quality audio signal and are now the popular choice in laboratory and recording studio applications. The inherent suitability of this technology is due to the very small mass that must be moved by the incident sound wave compared to other microphone types that require the sound wave to do more work. Condenser microphones require a power source, provided either via microphone inputs on equipment as phantom power or from

1848-492: A laser source travels through an optical fiber to illuminate the surface of a reflective diaphragm. Sound vibrations of the diaphragm modulate the intensity of light reflecting off the diaphragm in a specific direction. The modulated light is then transmitted over a second optical fiber to a photodetector, which transforms the intensity-modulated light into analog or digital audio for transmission or recording. Fiber-optic microphones possess high dynamic and frequency range, similar to

1980-546: A laser-photocell pair with a moving stream of smoke or vapor in the laser beam's path. Sound pressure waves cause disturbances in the smoke that in turn cause variations in the amount of laser light reaching the photodetector. A prototype of the device was demonstrated at the 127th Audio Engineering Society convention in New York City from 9 through October 12, 2009. Early microphones did not produce intelligible speech, until Alexander Graham Bell made improvements including

2112-499: A limiting function. This stage provides a constant level of signal to the FM demodulator stage, reducing the effect of input signal level changes to the output. If two or more signals are received at the same time, a high-performance limiter stage can greatly reduce the effect of the weaker signals on the output. This is commonly referred to as the FM capture effect . Generally, FM demodulators are not affected by amplitude variations, since

2244-453: A liquid microphone. The MEMS (microelectromechanical systems) microphone is also called a microphone chip or silicon microphone. A pressure-sensitive diaphragm is etched directly into a silicon wafer by MEMS processing techniques and is usually accompanied with an integrated preamplifier. Most MEMS microphones are variants of the condenser microphone design. Digital MEMS microphones have built-in analog-to-digital converter (ADC) circuits on

2376-411: A live performer. They are either of a universal fit or custom fit design. The universal fit in-ear monitors feature rubber or foam tips that can be inserted into virtually anybody's ear. Custom-fit in-ear monitors are created from an impression of the user's ear that has been made by an audiologist . In-ear monitors are almost always used in conjunction with a wireless transmitting system, allowing

2508-455: A microphone that a vocalist is singing into or a microphone placed in front of an instrument or guitar amplifier . These signal inputs are plugged into the input jacks of a thick multicore cable (often called a snake ). The snake then delivers the signals of all of the inputs to one or more mixing consoles . In a coffeehouse or small nightclub, the snake may be only routed to a single mixing console, which an audio engineer will use to adjust

2640-421: A noise gate, the threshold of sensitivity for each microphone on the drum kit can be set so that only the direct strike and subsequent decay of the drum will be heard, not the nearby sounds. Reverberation and delay effects are widely used in sound reinforcement systems to enhance the sound of the mix and create a desired artistic effect. Reverb and delay add a sense of spaciousness to the sound. Reverb can give

2772-448: A performer or a section of the stage. They are generally sent a different mix of vocals or instruments than the mix that is sent to the main loudspeaker system. Monitor loudspeaker cabinets are often a wedge shape, directing their output upwards towards the performer when set on the floor of the stage. Simple two-way, dual-driver designs with a speaker cone and a horn are common, as monitor loudspeakers need to be smaller to save space on

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2904-439: A person singing into an electric signal, signal processors which alter the signal characteristics (e.g., equalizers that adjust the bass and treble, compressors that reduce signal peaks, etc.), amplifiers , which produce a powerful version of the resulting signal that can drive a loudspeaker and output transducers (e.g., loudspeakers in speaker cabinets ), which convert the signal back into sound energy (the sound heard by

3036-457: A preamplifier and, therefore, do require phantom power, and circuits of modern passive ribbon microphones (i.e. those without the aforementioned preamplifier) are specifically designed to resist damage to the ribbon and transformer by phantom power. Also there are new ribbon materials available that are immune to wind blasts and phantom power. The carbon microphone was the earliest type of microphone. The carbon button microphone (or sometimes just

3168-405: A problem. Digital effects units may offer multiple pre-set and variable reverb, echo and related effects . Digital loudspeaker management systems offer sound engineers digital delay (to ensure speakers are in sync with each other), limiting, crossover functions, EQ filters, compression and other functions in a single rack-mountable unit. In previous decades, sound engineers typically had to transport

3300-410: A range of treatments designed to limit the maximum level of a signal. Treatments in order of decreasing severity range from clipping , in which a signal is passed through normally but sheared off when it would normally exceed a certain threshold; soft clipping which squashes peaks instead of shearing them; a hard limiter, a type of variable-gain audio level compression , in which the gain of an amplifier

3432-566: A separate stage monitor mixing console which is dedicated to creating mixes for the performers on-stage. These consoles are typically placed at the side of the stage so that the operator can communicate with the performers on stage. Small PA systems for venues such as bars and clubs are now available with features that were formerly only available on professional-level equipment, such as digital reverb effects, graphic equalizers , and, in some models, feedback prevention circuits which electronically sense and prevent audio feedback when it becomes

3564-417: A single unit are used to process the mix from the mixing console and route it to the various amplifiers. Systems may include several loudspeakers, each with its own output optimized for a specific range of frequencies (i.e. bass, midrange, and treble). Bi-amping and tri-amping of a sound reinforcement system with the aid of a DLMS results in more efficient use of amplifier power by sending each amplifier only

3696-497: A small public address (PA) system, consisting of, for example, a single microphone connected to a 100-watt amplified loudspeaker for a singer-guitarist playing in a small coffeehouse . In both cases, these systems reinforce sound to make it louder or distribute it to a wider audience. Some audio engineers and others in the professional audio industry disagree over whether these audio systems should be called sound reinforcement (SR) systems or PA systems. Distinguishing between

3828-414: A small battery. Power is necessary for establishing the capacitor plate voltage and is also needed to power the microphone electronics. Condenser microphones are also available with two diaphragms that can be electrically connected to provide a range of polar patterns , such as cardioid, omnidirectional, and figure-eight. It is also possible to vary the pattern continuously with some microphones, for example,

3960-598: A static charge is embedded in an electret by the alignment of the static charges in the material, much the way a permanent magnet is made by aligning the magnetic domains in a piece of iron. Due to their good performance and ease of manufacture, hence low cost, the vast majority of microphones made today are electret microphones; a semiconductor manufacturer estimates annual production at over one billion units. They are used in many applications, from high-quality recording and lavalier (lapel mic) use to built-in microphones in small sound recording devices and telephones. Prior to

4092-479: A substantial number of rack-mounted analog effects unit devices to accomplish these tasks. Equalizers are electronic devices that allow audio engineers to control the tone and frequencies of the sound in a channel, group (e.g., all the mics on a drumkit) or an entire stage's mix. The bass and treble controls on a home stereo are a simple type of equalizer. Equalizers exist in professional sound reinforcement systems in three forms: shelving equalizers (typically for

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4224-432: A thin, usually corrugated metal ribbon suspended in a magnetic field. The ribbon is electrically connected to the microphone's output, and its vibration within the magnetic field generates the electrical signal. Ribbon microphones are similar to moving coil microphones in the sense that both produce sound by means of magnetic induction. Basic ribbon microphones detect sound in a bi-directional (also called figure-eight, as in

4356-587: A useful by-product of which is that RF condenser microphones can be operated in damp weather conditions that could create problems in DC-biased microphones with contaminated insulating surfaces. The Sennheiser MKH series of microphones use the RF biasing technique. A covert, remotely energized application of the same physical principle called the Thing was devised by Soviet Russian inventor Leon Theremin and used to bug

4488-424: A variable-resistance microphone/transmitter. Bell's liquid transmitter consisted of a metal cup filled with water with a small amount of sulfuric acid added. A sound wave caused the diaphragm to move, forcing a needle to move up and down in the water. The electrical resistance between the wire and the cup was then inversely proportional to the size of the water meniscus around the submerged needle. Elisha Gray filed

4620-476: A very limited frequency response range but are very robust devices. The Boudet microphone, which used relatively large carbon balls, was similar to the granule carbon button microphones. Unlike other microphone types, the carbon microphone can also be used as a type of amplifier, using a small amount of sound energy to control a larger amount of electrical energy. Carbon microphones found use as early telephone repeaters , making long-distance phone calls possible in

4752-643: A very poor sound quality. The first microphone that enabled proper voice telephony was the (loose-contact) carbon microphone . This was independently developed by David Edward Hughes in England and Emile Berliner and Thomas Edison in the US. Although Edison was awarded the first patent in mid-1877 (after a long legal dispute), Hughes had demonstrated his working device in front of many witnesses some years earlier, and most historians credit him with its invention. The Berliner microphone found commercial success through

4884-413: A voltage when subjected to pressure—to convert vibrations into an electrical signal. An example of this is potassium sodium tartrate , which is a piezoelectric crystal that works as a transducer, both as a microphone and as a slimline loudspeaker component. Crystal microphones were once commonly supplied with vacuum tube (valve) equipment, such as domestic tape recorders. Their high output impedance matched

5016-460: A whole range of bass and treble frequencies), graphic equalizers and parametric equalizers . Graphic equalizers have faders (vertical slide controls) which together resemble a frequency response curve plotted on a graph. The faders can be used to boost or cut specific frequency bands. Using equalizers, frequencies that are too weak, such as a singer with modest projection in their lower register, can be boosted. Frequencies that are too loud, such as

5148-421: Is a function of frequency. The body of the microphone is not infinitely small and, as a consequence, it tends to get in its own way with respect to sounds arriving from the rear, causing a slight flattening of the polar response. This flattening increases as the diameter of the microphone (assuming it's cylindrical) reaches the wavelength of the frequency in question. Therefore, the smallest diameter microphone gives

5280-403: Is aimed at the surface of a window or other plane surface that is affected by sound. The vibrations of this surface change the angle at which the beam is reflected, and the motion of the laser spot from the returning beam is detected and converted to an audio signal. In a more robust and expensive implementation, the returned light is split and fed to an interferometer , which detects movement of

5412-555: Is at least one practical application that exploits those weaknesses: the use of a medium-size woofer placed closely in front of a "kick drum" ( bass drum ) in a drum set to act as a microphone. A commercial product example is the Yamaha Subkick, a 6.5-inch (170 mm) woofer shock-mounted into a 10" drum shell used in front of kick drums. Since a relatively massive membrane is unable to transduce high frequencies while being capable of tolerating strong low-frequency transients,

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5544-487: Is changed very quickly to prevent the signal from going over a certain amplitude or a soft limiter which reduces maximum output through gain compression . For military two-way radio sets and aircraft VHF voice telecommunications, the voice limiter is known as a vogad . It is designed to work with high levels of background noise near the microphone. One form operates by up-converting the audio signal to an ultrasonic frequency, hard limiting that signal, and then down converting

5676-595: Is intentional, so the sound engineer does not try to prevent it. A power amplifier is an electronic device that uses electrical power and circuitry to boost a line level signal and provides enough electrical power to drive a loudspeaker and produce sound. All loudspeakers, including headphones , require power amplification. Most professional audio power amplifiers also provide protection from clipping typically as some form of limiting . A power amplifier pushed into clipping can damage loudspeakers. Amplifiers also typically provide protection against short circuits across

5808-406: Is not relevant to the program, such as the hum of a miked electric guitar amplifier or the rustling of papers on a minister's lectern. Noise gates are also used to process the microphones placed near the drums of a drum kit in many hard rock and metal bands. Without a noise gate, the microphone for a specific instrument such as the floor tom will also pick up signals from nearby drums or cymbals. With

5940-399: Is practically constant and the voltage across the capacitor changes instantaneously to reflect the change in capacitance. The voltage across the capacitor varies above and below the bias voltage. The voltage difference between the bias and the capacitor is seen across the series resistor. The voltage across the resistor is amplified for performance or recording. In most cases, the electronics in

6072-402: Is quite subjective and is often collectively determined by a production's audio engineer, artists, bandleader , music producer , or musical director. A feedback suppressor detects unwanted audio feedback and suppresses it, typically by automatically inserting a notch filter into the signal path of the system. Audio feedback can create unwanted loud, screaming noises that are disruptive to

6204-478: Is the combination of microphones , signal processors , amplifiers , and loudspeakers in enclosures all controlled by a mixing console that makes live or pre-recorded sounds louder and may also distribute those sounds to a larger or more distant audience. In many situations, a sound reinforcement system is also used to enhance or alter the sound of the sources on the stage, typically by using electronic effects , such as reverb , as opposed to simply amplifying

6336-441: Is to sounds arriving at different angles about its central axis. The polar patterns illustrated above represent the locus of points in polar coordinates that produce the same signal level output in the microphone if a given sound pressure level (SPL) is generated from that point. How the physical body of the microphone is oriented relative to the diagrams depends on the microphone design. For large-membrane microphones such as in

6468-565: The Audio Engineering Society (AES) and the loudspeaker industry group ALMA in developing the EIA-426 testing standard, power-handling specifications became more trustworthy. Lightweight, portable speaker systems for small venues route the low-frequency parts of the music (electric bass, bass drum, etc.) to a powered subwoofer . Routing the low-frequency energy to a separate amplifier and subwoofer can substantially improve

6600-477: The Røde NT2000 or CAD M179. There are two main categories of condenser microphones, depending on the method of extracting the audio signal from the transducer: DC-biased microphones, and radio frequency (RF) or high frequency (HF) condenser microphones. With a DC-biased condenser microphone , the plates are biased with a fixed charge ( Q ). The voltage maintained across the capacitor plates changes with

6732-405: The diagram below) pattern because the ribbon is open on both sides. Also, because the ribbon has much less mass it responds to the air velocity rather than the sound pressure . Though the symmetrical front and rear pickup can be a nuisance in normal stereo recording, the high side rejection can be used to advantage by positioning a ribbon microphone horizontally, for example above cymbals, so that

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6864-401: The exciter and harmonizer . The use of effects in the reproduction of 2010-era pop music is often in an attempt to mimic the sound of the studio version of the artist's music in a live concert setting. For example, an audio engineer may use an Auto Tune effect to produce unusual vocal sound effects that a singer used on their recordings. The appropriate type, variation, and level of effects

6996-908: The stage monitor system . Microphones used for sound reinforcement are positioned and mounted in many ways, including base-weighted upright stands, podium mounts, tie-clips, instrument mounts, and headset mounts . Microphones on stands are also placed in front of instrument amplifiers to pick up the sound. Headset-mounted and tie-clip-mounted microphones are often used with wireless transmission to allow performers or speakers to move freely. Early adopters of headset mounted microphones technology included country singer Garth Brooks , Kate Bush , and Madonna . Other types of input transducers include magnetic pickups used in electric guitars and electric basses, contact microphones used on stringed instruments, and pianos and phonograph pickups (cartridges) used in record players. Electronic instruments such as synthesizers can have their output signal routed directly to

7128-406: The 2010s, there has been increased interest and research into making piezoelectric MEMS microphones which are a significant architectural and material change from existing condenser style MEMS designs. In a plasma microphone, a plasma arc of ionized gas is used. The sound waves cause variations in the pressure around the plasma in turn causing variations in temperature which alter the conductance of

7260-463: The English physicist Robert Hooke was the first to experiment with a medium other than air with the invention of the " lovers' telephone " made of stretched wire with a cup attached at each end. In 1856, Italian inventor Antonio Meucci developed a dynamic microphone based on the generation of electric current by moving a coil of wire to various depths in a magnetic field. This method of modulation

7392-515: The Oktava (pictured above), the upward direction in the polar diagram is usually perpendicular to the microphone body, commonly known as "side fire" or "side address". For small diaphragm microphones such as the Shure (also pictured above), it usually extends from the axis of the microphone commonly known as "end fire" or "top/end address". Some microphone designs combine several principles in creating

7524-608: The US Ambassador's residence in Moscow between 1945 and 1952. An electret microphone is a type of condenser microphone invented by Gerhard Sessler and Jim West at Bell laboratories in 1962. The externally applied charge used for a conventional condenser microphone is replaced by a permanent charge in an electret material. An electret is a ferroelectric material that has been permanently electrically charged or polarized . The name comes from electrostatic and magnet ;

7656-414: The air pressure variations of a sound wave to an electrical signal. The most common are the dynamic microphone , which uses a coil of wire suspended in a magnetic field; the condenser microphone , which uses the vibrating diaphragm as a capacitor plate; and the contact microphone , which uses a crystal of piezoelectric material. Microphones typically need to be connected to a preamplifier before

7788-420: The audience and the performers). These primary parts involve varying numbers of individual components to achieve the desired goal of reinforcing and clarifying the sound to the audience, performers, or other individuals. Sound reinforcement in a large format system typically involves a signal path that starts with the signal inputs, which may be instrument pickups (on an electric guitar or electric bass ) or

7920-832: The back wall of the stage out into vocal mics and the audience, which improves the clarity of the front-of-house mix. Sound reinforcement systems are used in a broad range of different settings, each of which poses different challenges. Audio-visual rental systems have to be able to withstand heavy use and even abuse from renters. For this reason, rental companies tend to own speaker cabinets that are heavily braced and protected with steel corners, and electronic equipment such as power amplifiers or effects are often mounted into protective road cases. Rental companies also tend to select gear that have electronic protection features, such as speaker-protection circuitry and amplifier limiters. Rental systems for non-professionals need to be easy to use and set up and they must be easy to repair and maintain for

8052-421: The baseband is contained in the frequency deviations . Some detectors, including the ratio detector , inherently limit gain by the nature of the circuit design. In AM radio , the information is located in the amplitude variations, and distortion can occur due to spurious signals that could cause the baseband to be misrepresented. In Canada , while the cold weather rule is in effect, limiters are used to lower

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8184-577: The bass response of the system. Also, clarity may be enhanced because low-frequency sounds can cause intermodulation and other distortion in speaker systems. Professional sound reinforcement speaker systems often include dedicated hardware for safely flying them above the stage area, to provide more even sound coverage and to maximize sightlines within performance venues. Monitor loudspeakers , also called foldback loudspeakers, are speaker cabinets used onstage to help performers to hear their singing or playing. As such, monitor speakers are pointed towards

8316-619: The best high fidelity conventional microphones. Fiber-optic microphones do not react to or influence any electrical, magnetic, electrostatic or radioactive fields (this is called EMI/RFI immunity). The fiber-optic microphone design is therefore ideal for use in areas where conventional microphones are ineffective or dangerous, such as inside industrial turbines or in magnetic resonance imaging (MRI) equipment environments. Fiber-optic microphones are robust, resistant to environmental changes in heat and moisture, and can be produced for any directionality or impedance matching . The distance between

8448-472: The best omnidirectional characteristics at high frequencies. The wavelength of sound at 10 kHz is 1.4" (3.5 cm). The smallest measuring microphones are often 1/4" (6 mm) in diameter, which practically eliminates directionality even up to the highest frequencies. Omnidirectional microphones, unlike cardioids, do not employ resonant cavities as delays, and so can be considered the "purest" microphones in terms of low coloration; they add very little to

8580-457: The capacity of houses of non-paying customers. The limiters allow enough power to run a furnace and a few lights. Tampering with the limiter is illegal. [REDACTED]  This article incorporates public domain material from Federal Standard 1037C . General Services Administration . Archived from the original on 2022-01-22.  (in support of MIL-STD-188 ). Sound reinforcement system A sound reinforcement system

8712-407: The capsule (around 5 to 100  pF ) and the value of the bias resistor (100  MΩ to tens of GΩ) form a filter that is high-pass for the audio signal, and low-pass for the bias voltage. Note that the time constant of an RC circuit equals the product of the resistance and capacitance. Within the time frame of the capacitance change (as much as 50 ms at 20 Hz audio signal), the charge

8844-759: The cooling capabilities of the amplifier. In the 1970s and 1980s, most PAs employed heavy class AB amplifiers . In the late 1990s, power amplifiers in PA applications became lighter, smaller, more powerful, and more efficient, with the increasing use of switching power supplies and class D amplifiers , which offered significant weight- and space-savings as well as increased efficiency. Often installed in railroad stations, stadia, and airports, class D amplifiers can run with minimal additional cooling and with higher rack densities, compared to older amplifiers. Digital loudspeaker management systems (DLMS) that combine digital crossover functions, compression, limiting, and other features in

8976-425: The desired polar pattern. This ranges from shielding (meaning diffraction/dissipation/absorption) by the housing itself to electronically combining dual membranes. An omnidirectional (or nondirectional) microphone's response is generally considered to be a perfect sphere in three dimensions. In the real world, this is not the case. As with directional microphones, the polar pattern for an "omnidirectional" microphone

9108-515: The different frequencies to the appropriate drivers. In the 1960s, horn loaded theater and PA speakers were commonly columns of multiple drivers mounted in a vertical line within a tall enclosure. The 1970s to early 1980s was a period of innovation in loudspeaker design with many sound reinforcement companies designing their own speakers using commercially available drivers. The areas of innovation were in cabinet design, durability, ease of packing and transport, and ease of setup. This period also saw

9240-490: The distance between the plates. Because the capacitance of the plates is inversely proportional to the distance between them, the vibrations produce changes in capacitance. These changes in capacitance are used to measure the audio signal . The assembly of fixed and movable plates is called an element or capsule . Condenser microphones span the range from telephone mouthpieces through inexpensive karaoke microphones to high-fidelity recording microphones. They generally produce

9372-531: The effect of singing voice or instrument being present in anything from a small room to a massive hall, or even in a space that does not exist in the physical world. The use of reverb often goes unnoticed by the audience, as it often sounds more natural than if the signal was left "dry" (without effects). Many modern mixing boards designed for live sound include on-board reverb effects. Other effects include modulation effects such as Flanger , phaser , and chorus and spectral manipulation or harmonic effects such as

9504-486: The effective dynamic range of ribbon microphones at low frequencies. Protective wind screens can reduce the danger of damaging a vintage ribbon, and also reduce plosive artifacts in the recording. Properly designed wind screens produce negligible treble attenuation. In common with other classes of dynamic microphone, ribbon microphones do not require phantom power; in fact, this voltage can damage some older ribbon microphones. Some new modern ribbon microphone designs incorporate

9636-466: The era before vacuum tubes. Called a Brown's relay, these repeaters worked by mechanically coupling a magnetic telephone receiver to a carbon microphone: the faint signal from the receiver was transferred to the microphone, where it modulated a stronger electric current, producing a stronger electrical signal to send down the line. A crystal microphone or piezo microphone uses the phenomenon of piezoelectricity —the ability of some materials to produce

9768-399: The feedback. Dynamic range compression is designed to help the audio engineer to manage the dynamic range of audio signals. Prior to the invention of automatic compressors, audio engineers accomplished the same goal by "riding the faders", listening carefully to the mix and lowering the faders of any singer or instrument which was getting too loud. A compressor accomplishes this by reducing

9900-441: The frequencies appropriate for its respective loudspeaker and eliminating losses associated with passive crossover circuits. A simple and inexpensive PA loudspeaker may have a single full-range loudspeaker driver , housed in a suitable enclosure. More elaborate, professional-caliber sound reinforcement loudspeakers may incorporate separate drivers to produce low, middle, and high frequency sounds. A crossover network routes

10032-409: The gain of a signal that is above a defined level (the threshold) by a defined amount determined by the ratio setting. Most compressors available are designed to allow the operator to select a ratio within a range typically between 1:1 and 20:1, with some allowing settings of up to ∞:1. A compressor with high compression ratio is typically referred to as a limiter . The speed that the compressor adjusts

10164-423: The gain of the signal ( attack and release ) is typically adjustable as is the final output or make-up gain of the device. Compressor applications vary widely. Some applications use limiters for component protection and gain structure control. Artistic signal manipulation using a compressor is a subjective technique widely utilized by mix engineers to improve clarity or to creatively alter the signal in relation to

10296-413: The granules, causing the contact area between each pair of adjacent granules to change, and this causes the electrical resistance of the mass of granules to change. The changes in resistance cause a corresponding change in the current flowing through the microphone, producing the electrical signal. Carbon microphones were once commonly used in telephones; they have extremely low-quality sound reproduction and

10428-465: The heart of a sound reinforcement system. This is where the sound engineer can adjust the volume and tone of each input, whether it is a vocalist's microphone or the signal from an electric bass , and mix, equalize and add effects to these sound sources. Doing the mixing for a live show requires a mix of technical and artistic skills. A sound engineer needs to have an expert knowledge of speaker and amplifier set-up, effects units and other technologies and

10560-770: The high input impedance (typically about 10 MΩ) of the vacuum tube input stage well. They were difficult to match to early transistor equipment and were quickly supplanted by dynamic microphones for a time, and later small electret condenser devices. The high impedance of the crystal microphone made it very susceptible to handling noise, both from the microphone itself and from the connecting cable. Piezoelectric transducers are often used as contact microphones to amplify sound from acoustic musical instruments, to sense drum hits, for triggering electronic samples, and to record sound in challenging environments, such as underwater under high pressure. Saddle-mounted pickups on acoustic guitars are generally piezoelectric devices that contact

10692-496: The implementation. Many sound reinforcement loudspeaker systems incorporate protection circuitry to prevent damage from excessive power or operator error. Resettable fuses , specialized current-limiting light bulbs, and circuit breakers were used alone or in combination to reduce driver failures. During the same period, the professional sound reinforcement industry made the Neutrik Speakon NL4 and NL8 connectors

10824-426: The in-ear monitor sends. Since their introduction in the mid-1980s, in-ear monitors have grown to be the most popular monitoring choice for large touring acts. The reduction or elimination of loudspeakers other than instrument amplifiers on stage has allowed for cleaner and less problematic mixing for both the front of house and monitor engineers. Audio feedback is greatly reduced and there is less sound reflecting off

10956-405: The in-ear monitors of one performer cannot be heard by the other musicians. A downside of this isolation is that the performer cannot hear the crowd or the comments from other performers on stage that do not have microphones (e.g., if the bass player wishes to communicate to the drummer). This has been remedied in larger productions by setting up microphones facing the audience that can be mixed into

11088-513: The internal baffle, allowing the selection of several response patterns ranging from "figure-eight" to "unidirectional". Such older ribbon microphones, some of which still provide high-quality sound reproduction, were once valued for this reason, but a good low-frequency response could be obtained only when the ribbon was suspended very loosely, which made them relatively fragile. Modern ribbon materials, including new nanomaterials , have now been introduced that eliminate those concerns and even improve

11220-415: The introduction of the hanging or flying of main loudspeakers at large concerts. During the 1980s the large speaker manufacturers started producing standard products using the innovations of the 1970s. These were mostly smaller two way systems with 12", 15" or double 15" woofers and a high frequency driver attached to a high frequency horn. The 1980s also saw the start of loudspeaker companies focused on

11352-486: The main mix for the audience at FOH and another to do the monitor mix for the performers on stage. Once the signal arrives at an input on a mixing console, this signal can be adjusted in many ways by the sound engineer. A signal can be equalized (e.g., by adjusting the bass or treble of the sound), compressed (to avoid unwanted signal peaks), or panned (that is sent to the left or right speakers). The signal may also be routed into an external effects processor , such as

11484-737: The main outputs are often sent to an additional equalizer, or directly to a power amplifier , with one or more loudspeakers (typically two, one on each side of the stage in smaller venues, or a large number in big venues) that are connected to that amplifier. In large-format systems, the signal is typically first routed through an equalizer then to a crossover . A crossover splits the signal into multiple frequency bands with each band being sent to separate amplifiers and speaker enclosures for low, middle, and high-frequency signals. Low-frequency signals are sent to amplifiers and then to subwoofers , and middle and high-frequency sounds are typically sent to amplifiers which power full-range speaker cabinets. Using

11616-423: The microphone itself contribute no voltage gain as the voltage differential is quite significant, up to several volts for high sound levels. RF condenser microphones use a comparatively low RF voltage, generated by a low-noise oscillator. The signal from the oscillator may either be amplitude modulated by the capacitance changes produced by the sound waves moving the capsule diaphragm, or the capsule may be part of

11748-489: The microphone's light source and its photodetector may be up to several kilometers without need for any preamplifier or another electrical device, making fiber-optic microphones suitable for industrial and surveillance acoustic monitoring. Fiber-optic microphones are used in very specific application areas such as for infrasound monitoring and noise cancellation . They have proven especially useful in medical applications, such as allowing radiologists, staff and patients within

11880-414: The mid-range frequencies. They are also available as separate rack-mount units that can be connected to a mixing board. Parametric equalizers typically use knobs and sometimes buttons. The audio engineer can select which frequency band to cut or boost, and then use additional knobs to adjust how much to cut or boost this frequency range. Parametric equalizers first became popular in the 1970s and have remained

12012-401: The mixing console. A DI unit may be necessary to adapt some of these sources to the inputs of the console. Wireless systems are typically used for electric guitar, bass, handheld microphones and in-ear monitor systems. This lets performers move about the stage during the show or even go out into the audience without the worry of tripping over or disconnecting cables. Mixing consoles are

12144-434: The most commonly used input device. Microphones can be classified according to their method of transduction, polar pattern or their functional application. Most microphones used in sound reinforcement are either dynamic or condenser microphones. One type of directional microphone, called cardioid mics, are widely used in live sound, because they reduce pickup from the side and rear, helping to avoid unwanted feedback from

12276-511: The next breakthrough with the first condenser microphone . In 1923, the first practical moving coil microphone was built. The Marconi-Sykes magnetophone, developed by Captain H. J. Round , became the standard for BBC studios in London. This was improved in 1930 by Alan Blumlein and Herbert Holman who released the HB1A and was the best standard of the day. Also in 1923, the ribbon microphone

12408-542: The output and overheating. Audio engineers select amplifiers that provide enough headroom . Headroom refers to the amount by which the signal-handling capabilities of an audio system exceed a designated nominal level . Headroom can be thought of as a safety zone allowing transient audio peaks to exceed the nominal level without damaging the system or the audio signal, e.g., via clipping . Standards bodies differ in their recommendations for nominal level and headroom. Selecting amplifiers with enough headroom helps to ensure that

12540-424: The performance, and can damage speakers and performers' and audience members' ears. Audio feedback from microphones occurs when a microphone is too near a monitor or main speaker and the sound reinforcement system amplifies itself. Audio feedback through a microphone is almost universally regarded as a negative phenomenon, many electric guitarists use guitar feedback as part of their performance. This type of feedback

12672-404: The performer to freely move about the stage while receiving their monitor mix. In-ear monitors offer considerable isolation for the performer using them: no on-stage sound is heard and the monitor engineer can deliver a much more accurate and clear mix for the performer. With in-ear monitors, each performer can be sent their own customized mix; although this was also the case with monitor speakers,

12804-501: The performers in front of them. The clarity of the mix for the performer on stage is also typically compromised as they hear more extraneous noise from around them. The use of monitor loudspeakers, active (with an integrated amplifier) or passive, requires more cabling and gear on stage, resulting in a more cluttered stage. These factors, amongst others, have led to the increasing popularity of in-ear monitors. In-ear monitors are headphones that have been designed for use as monitors by

12936-495: The plasma. These variations in conductance can be picked up as variations superimposed on the electrical supply to the plasma. This is an experimental form of microphone. A loudspeaker, a transducer that turns an electrical signal into sound waves, is the functional opposite of a microphone. Since a conventional speaker is similar in construction to a dynamic microphone (with a diaphragm, coil and magnet), speakers can actually work "in reverse" as microphones. Reciprocity applies, so

13068-459: The power amplifier and to protect speakers. Electric guitar amps do not usually have limiters. PIN diodes can be used in limiter circuits to reflect the energy back to the source or clip the signal. Mastering engineers often use limiting combined with make-up gain to increase the perceived loudness of an audio recording during the audio mastering process. An FM radio receiver usually has at least one stage of amplification that performs

13200-471: The powerful and noisy magnetic field to converse normally, inside the MRI suites as well as in remote control rooms. Other uses include industrial equipment monitoring and audio calibration and measurement, high-fidelity recording and law enforcement. Laser microphones are often portrayed in movies as spy gadgets because they can be used to pick up sound at a distance from the microphone equipment. A laser beam

13332-415: The principal sound input to the principal axis (end- or side-address) of the microphone are used to describe the microphone. The condenser microphone , invented at Western Electric in 1916 by E. C. Wente, is also called a capacitor microphone or electrostatic microphone —capacitors were historically called condensers. The diaphragm acts as one plate of a capacitor, and audio vibrations produce changes in

13464-446: The program equalizer of choice for many engineers since then. A high-pass (low-cut) and/or low-pass (high-cut) filter may also be included on equalizers or audio consoles. High-pass and low-pass filters restrict a given channel's bandwidth extremes. Cutting very low-frequency sound signals (termed infrasonic , or subsonic ) reduces the waste of amplifier power which does not produce audible sound and which moreover can be hard on

13596-427: The program material. An example of artistic compression is the typical heavy compression used on the various components of a modern rock drum kit. The drums are processed to be perceived as sounding more punchy and full. A noise gate mutes signals below a set threshold level. A noise gate's function is in, a sense, opposite to that of a compressor. Noise gates are useful for microphones which will pick up noise that

13728-474: The proliferation of MEMS microphones, nearly all cell-phone, computer, PDA and headset microphones were electret types. Unlike other capacitor microphones, they require no polarizing voltage, but often contain an integrated preamplifier that does require power. This preamplifier is frequently phantom powered in sound reinforcement and studio applications. Monophonic microphones designed for personal computers (PCs), sometimes called multimedia microphones, use

13860-451: The rear lobe picks up sound only from the cymbals. Crossed figure 8, or Blumlein pair , stereo recording is gaining in popularity, and the figure-eight response of a ribbon microphone is ideal for that application. Other directional patterns are produced by enclosing one side of the ribbon in an acoustic trap or baffle, allowing sound to reach only one side. The classic RCA Type 77-DX microphone has several externally adjustable positions of

13992-1047: The rental company that tour with the band to set up and calibrate the equipment. The individual that mixes the band is often selected and provided by the band, as they are familiar with the various aspects of the show and understand how the band wants the show to sound. Microphone A microphone , colloquially called a mic ( / m aɪ k / ), or mike , is a transducer that converts sound into an electrical signal . Microphones are used in many applications such as telephones , hearing aids , public address systems for concert halls and public events, motion picture production, live and recorded audio engineering , sound recording , two-way radios , megaphones , and radio and television broadcasting. They are also used in computers and other electronic devices, such as mobile phones , for recording sounds, speech recognition , VoIP , and other purposes, such as ultrasonic sensors or knock sensors . Several types of microphone are used today, which employ different methods to convert

14124-465: The renting company. From this perspective, speaker cabinets need to have easy-to-access horns, speakers, and crossover circuitry, so that repairs or replacements can be made. Many touring acts and large venue corporate events will rent large sound reinforcement systems that typically include one or more audio engineers on staff with the renting company. In the case of rental systems for tours, there are typically several audio engineers and technicians from

14256-459: The requirements of the loudspeaker. Some active loudspeakers also have equalization, crossover and mixing circuitry built in. Since amplifiers can generate a significant amount of heat, thermal dissipation is an important factor for operators to consider when mounting amplifiers into equipment racks. Many power amplifiers feature internal fans to draw air across their heat sinks. The heat sinks can become clogged with dust, which can adversely affect

14388-603: The result. The frequency conversion uses image-cancelling heterodyning. The advantage of clipping the supersonic signal is that the odd harmonics produced will still be out-of-band when down converted. This is in contrast to standard hard limiting, as in an electric guitar fuzz box, where the harmonics are highly audible. This device ultimately gives a distinctive character to the voice communication, which despite being highly distorted, ensures spoken words remain clear. Bass instrument amplifiers and power amplifiers are more commonly equipped with limiter circuitry to prevent overloading

14520-461: The resulting microphone has the same impairments as a single-driver loudspeaker: limited low- and high-end frequency response, poorly controlled directivity , and low sensitivity . In practical use, speakers are sometimes used as microphones in applications where high bandwidth and sensitivity are not needed such as intercoms , walkie-talkies or video game voice chat peripherals, or when conventional microphones are in short supply. However, there

14652-498: The same CMOS chip making the chip a digital microphone and so more readily integrated with modern digital products. Major manufacturers producing MEMS silicon microphones are Wolfson Microelectronics (WM7xxx) now Cirrus Logic, InvenSense (product line sold by Analog Devices ), Akustica (AKU200x), Infineon (SMM310 product), Knowles Electronics, Memstech (MSMx), NXP Semiconductors (division bought by Knowles ), Sonion MEMS, Vesper, AAC Acoustic Technologies, and Omron. More recently, since

14784-436: The same dynamic principle as in a loudspeaker , only reversed. A small movable induction coil , positioned in the magnetic field of a permanent magnet, is attached to the diaphragm. When sound enters through the windscreen of the microphone, the sound wave moves the diaphragm which moves the coil in the magnetic field, producing a varying voltage across the coil through electromagnetic induction. Ribbon microphones use

14916-435: The second use of aux sends is to send all of the vocal signals from a rock band through a reverb effect. While reverb is usually added to vocals in the main mix, it is not usually added to electric bass and other rhythm section instruments. The processed input signals are then mixed to the master faders on the console. The next step in the signal path generally depends on the size of the system in place. In smaller systems,

15048-538: The side because sound arriving at the front and back at the same time creates no gradient between the two. The characteristic directional pattern of a pure pressure-gradient microphone is like a figure-8. Other polar patterns are derived by creating a capsule that combines these two effects in different ways. The cardioid, for instance, features a partially closed backside, so its response is a combination of pressure and pressure-gradient characteristics. A microphone's directionality or polar pattern indicates how sensitive it

15180-403: The signal can be recorded or reproduced . In order to speak to larger groups of people, a need arose to increase the volume of the human voice. The earliest devices used to achieve this were acoustic megaphones. Some of the first examples, from fifth-century-BC Greece, were theater masks with horn-shaped mouth openings that acoustically amplified the voice of actors in amphitheaters . In 1665,

15312-409: The signal will remain clean and undistorted. Like most sound reinforcement equipment, professional power amplifiers are typically designed to be mounted within standard 19-inch racks . Rack-mounted amps are typically housed in road cases to prevent damage to the equipment during transportation. Active loudspeakers have internally mounted amplifiers that have been selected by the manufacturer to match

15444-478: The sound and volume of the onstage vocals and instruments that the audience hears through the main speakers and adjust the volume of the monitor speakers that are aimed at the performers. Mid- to large-size performing venues typically route the onstage signals to two mixing consoles : the front of house (FOH), and the stage monitor system , which is often a second mixer at the side of the stage. In these cases, at least two audio engineers are required; one to do

15576-672: The sound reinforcement market. The 1990s saw the introduction of line arrays , where long vertical arrays of loudspeakers in smaller cabinets are used to increase efficiency and provide even dispersion and frequency response. Trapezoidal -shaped enclosures became popular as this shape allowed many of them to be easily arrayed together. This period also saw the introduction of inexpensive molded plastic speaker enclosures mounted on tripod stands. Many feature built-in power amplifiers which made them practical for non-professionals to set up and operate successfully. The sound quality available from these simple powered speakers varies widely depending on

15708-417: The sources unaltered. A sound reinforcement system for a rock concert in a stadium may be very complex, including hundreds of microphones, complex live sound mixing and signal processing systems, tens of thousands of watts of amplifier power, and multiple loudspeaker arrays , all overseen by a team of audio engineers and technicians. On the other hand, a sound reinforcement system can be as simple as

15840-438: The speaker is often ideal for picking up the kick drum while reducing bleed from the nearby cymbals and snare drums. The inner elements of a microphone are the primary source of differences in directivity. A pressure microphone uses a diaphragm between a fixed internal volume of air and the environment and responds uniformly to pressure from all directions, so it is said to be omnidirectional. A pressure-gradient microphone uses

15972-618: The stage. These loudspeakers typically require less power and volume than the main loudspeaker system, as they only need to provide sound for a few people who are in relatively close proximity to the loudspeaker. Some manufacturers have designed loudspeakers for use either as a component of a small PA system or as a monitor loudspeaker. A number of manufacturers produce powered monitor speakers , which contain an integrated amplifier. Using monitor speakers instead of in-ear monitors typically results in an increase of stage volume, which can lead to more feedback issues and progressive hearing damage for

16104-411: The standard speaker connectors, replacing 1/4" jacks , XLR connectors , and Cannon multipin connectors which are all limited to a maximum of 15 amps of current. XLR connectors are still the standard input connector on active loudspeaker cabinets. To help users avoid overpowering them, loudspeakers have a power rating (in watts ) which indicates their maximum power capacity. Thanks to the efforts of

16236-479: The strings passing over the saddle. This type of microphone is different from magnetic coil pickups commonly visible on typical electric guitars , which use magnetic induction, rather than mechanical coupling, to pick up vibration. A fiber-optic microphone converts acoustic waves into electrical signals by sensing changes in light intensity, instead of sensing changes in capacitance or magnetic fields as with conventional microphones. During operation, light from

16368-399: The subwoofer drivers. A low-pass filter to cut ultrasonic energy is useful to prevent interference from radio frequencies, lighting control, or digital circuitry creeping into the power amplifiers. Such filters are often paired with graphic and parametric equalizers to give the audio engineer full control of the frequency range. High-pass filters and low-pass filters used together function as

16500-423: The surface by changes in the optical path length of the reflected beam. The former implementation is a tabletop experiment; the latter requires an extremely stable laser and precise optics. A new type of laser microphone is a device that uses a laser beam and smoke or vapor to detect sound vibrations in free air. On August 25, 2009, U.S. patent 7,580,533 issued for a Particulate Flow Detection Microphone based on

16632-530: The two terms by technology and capability is common, while others distinguish by intended use (e.g., SR systems are for live event support and PA systems are for reproduction of speech and recorded music in buildings and institutions). In some regions or markets, the distinction between the two terms is important, though the terms are considered interchangeable in many professional circles. A typical sound reinforcement system consists of; input transducers (e.g., microphones ), which convert sound energy such as

16764-563: The use by Alexander Graham Bell for his telephone and Berliner became employed by Bell. The carbon microphone was critical in the development of telephony, broadcasting and the recording industries. Thomas Edison refined the carbon microphone into his carbon-button transmitter of 1886. This microphone was employed at the first radio broadcast ever, a performance at the New York Metropolitan Opera House in 1910. In 1916, E.C. Wente of Western Electric developed

16896-403: The vibrations in the air, according to the capacitance equation (C = Q ⁄ V ), where Q = charge in coulombs , C = capacitance in farads and V = potential difference in volts . A nearly constant charge is maintained on the capacitor. As the capacitance changes, the charge across the capacitor does change very slightly, but at audible frequencies it is sensibly constant. The capacitance of

17028-462: The word." In 1861, German inventor Johann Philipp Reis built an early sound transmitter (the " Reis telephone ") that used a metallic strip attached to a vibrating membrane that would produce intermittent current. Better results were achieved in 1876 with the " liquid transmitter " design in early telephones from Alexander Graham Bell and Elisha Gray – the diaphragm was attached to a conductive rod in an acid solution. These systems, however, gave

17160-652: Was a demand for high-fidelity microphones and greater directionality. Electro-Voice responded with their Academy Award -winning shotgun microphone in 1963. During the second half of the 20th century, development advanced quickly with the Shure Brothers bringing out the SM58 and SM57 . Microphones are categorized by their transducer principle (condenser, dynamic, etc.) and by their directional characteristics (omni, cardioid, etc.). Sometimes other characteristics such as diaphragm size, intended use or orientation of

17292-428: Was also the most enduring method for the technology of the telephone as well. Speaking of his device, Meucci wrote in 1857, "It consists of a vibrating diaphragm and an electrified magnet with a spiral wire that wraps around it. The vibrating diaphragm alters the current of the magnet. These alterations of current, transmitted to the other end of the wire, create analogous vibrations of the receiving diaphragm and reproduce

17424-399: Was introduced, another electromagnetic type, believed to have been developed by Harry F. Olson , who applied the concept used in a ribbon speaker to making a microphone. Over the years these microphones were developed by several companies, most notably RCA that made large advancements in pattern control, to give the microphone directionality. With television and film technology booming there

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